Microneedle Device

ABSTRACT

The present invention provides a microneedle device comprising: a substrate; a microneedle disposed on the substrate; and a coating layer formed on the microneedle; wherein the coating layer comprises a physiologically active substance, arginine, and glycerin.

TECHNICAL FIELD

The present invention relates to a microneedle device.

BACKGROUND ART

A microneedle device is known as one of the devices for intradermaladministration of a physiologically active substance. The microneedledevice has a plurality of microneedles on its main surface. As onespecific aspect thereof, for example, there is a microneedle having acoating layer containing a physiologically active substance formedthereon and a self-dissolving microneedle containing a physiologicallyactive substance (for example, Patent Literatures 1 to 4).

CITATION LIST Patent Literature

-   Patent Literature 1: WO 2011/105496-   Patent Literature 2: WO 2012/115207-   Patent Literature 3: WO 2012/115208-   Patent Literature 4: JP 2014-507473 A

SUMMARY OF INVENTION Technical Problem

In the case of a microneedle device in which a coating layer containinga physiologically active substance is formed on each microneedle, it isdifficult to reproducibly apply the physiologically active substance tothe coating layer of each microneedle so that the content of thesubstance is uniform.

When a coating agent is applied to form a coating layer, the coatinglayer may be cracked due to the components in the coating agent. Thus,it may be difficult to obtain sufficient strength for applying to theskin.

Therefore, an object of the present invention is to provide amicroneedle device having a coating layer in which coating can beperformed so that a physiologically active substance in the coatinglayer is uniformly dispersed and the occurrence of cracks in the coatinglayer can be reduced when the coating layer is formed.

Solution to Problem

The present invention provides a microneedle device comprising: asubstrate; a microneedle disposed on the substrate; and a coating layerformed on the microneedle; wherein the coating layer contains aphysiologically active substance, arginine, and glycerin.

The coating layer contains glycerin so that the same amount of thephysiologically active substance can be reproducibly applied to themicroneedles.

It is preferable that, in the coating layer, the mass of arginine is0.06 to 0.85-fold of the mass of the physiologically active substanceand the mass of glycerin is 40% or less relative to the mass of thewhole coating layer. It is preferable that the coating layer furthercontains an acid selected from the group consisting of citric acid,phosphoric acid, boric acid, tartaric acid, and lactic acid.

Further, the present invention provides a method for producing amicroneedle device including the steps of: providing a microneedle arrayhaving a substrate and a microneedle; mixing a physiologically activesubstance, arginine, and glycerin to obtain a coating composition;coating the microneedle with the coating composition; and drying thecoating composition to form a coating layer on the microneedle.

It is preferable that the coating composition further contains an acidselected from the group consisting of citric acid, phosphoric acid,boric acid, tartaric acid, and lactic acid.

It is preferable that the drying is performed until, in the coatinglayer, the mass of arginine reaches 0.06 to 0.85-fold of the mass of thephysiologically active substance and the mass of glycerin reaches 40% orless relative to the mass of the whole coating layer.

Further, the present invention provides a coating agent for microneedlescontaining a physiologically active substance, arginine, and glycerin.It is preferable that the coating agent further contains an acidselected from the group consisting of citric acid, phosphoric acid,boric acid, tartaric acid, and lactic acid.

The present invention also provides a method comprising a step ofcoating each microneedle with a coating composition containing aphysiologically active substance, arginine, and glycerin to form acoating layer, wherein the occurrence of cracks in the coating layer oneach microneedle is reduced. It is preferable that the coatingcomposition further contains an acid selected from the group consistingof citric acid, phosphoric acid, boric acid, tartaric acid, and lacticacid.

The present invention also provides a method comprising a step ofcoating each microneedle with a coating composition containing aphysiologically active substance, arginine, and glycerin to form acoating layer, wherein the content of the components contained in thecoating layer on each microneedle is uniformly dispersed. It ispreferable that the coating composition further contains an acidselected from the group consisting of citric acid, phosphoric acid,boric acid, tartaric acid, and lactic acid.

Advantageous Effects of Invention

According to the present invention, the same amount of thephysiologically active substance can be reproducibly applied to themicroneedles. Further, according to the present invention, when thecoating layer is formed, the occurrence of cracks of the coating layercan be reduced, thereby improving the productivity of the microneedledevice.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing one embodiment of a microneedledevice.

FIG. 2 is a cross-sectional side surface view of FIG. 1 taken along theline II-II.

FIGS. 3(a) to 3(c) are pattern diagrams showing one embodiment of amethod for producing a microneedle device.

DESCRIPTION OF EMBODIMENTS

Hereinbelow, preferable embodiments will be explained with reference todrawings. It is to be noted that in the explanation of the drawings, thesame symbols are assigned to the same elements and redundant explanationwill be omitted. Also, in the drawings, some parts are exaggeratedlydrawn to make understanding easy, and thus the size and ratio are notnecessarily consistent with the description.

One embodiment of the present invention is a microneedle devicecomprising: a substrate; a microneedle disposed on the substrate; and acoating layer formed on the microneedle; wherein the coating layercontains a physiologically active substance, arginine, and glycerin.

FIG. 1 is a perspective view showing one embodiment of a microneedledevice. A microneedle device 1 shown in FIG. 1 has a substrate 2, aplurality of microneedles 3 that are two-dimensionally arranged on thesubstrate 2, and a coating layer 5 formed on each of the microneedles 3.The coating layer 5 contains a physiologically active substance,arginine, and glycerin.

The substrate 2 is a foundation to support the microneedles 3. The areaof the substrate 2 is preferably 0.5 to 10 cm², more preferably 1 to 5cm², and still more preferably 1 to 3 cm². A substrate of a desired sizemay be configured by connecting a plurality of the substrates 2.

The microneedles 3 each have a minute structure, and the height (length)thereof is preferably 50 to 600 μm. At this point, the length of themicroneedles 3 is set at 50 μm or more, thereby ensuring administrationof the physiologically active substance contained in the coating layer.Further, the length of the microneedles 3 is set at 600 μm or less,thereby avoiding that the microneedles contact nerves so as to reducethe possibility of pain and avoid the possibility of bleeding. Also,when the length of the microneedles 3 is 500 μm or less, the amount ofthe physiologically active substance to enter the skin can beefficiently administered, and in certain cases, administrating withoutpiercing the basement membrane is also possible. The length of themicroneedles 3 is particularly preferably 300 to 500 μm.

At this point, a microneedle 3 refers to a projecting structureincluding, in a broad sense, a needle shape or a structure including aneedle shape. However, the microneedle is not limited to a structure ofa needle shape having a tapered tip, and may also be a structure lackinga tapered tip. When the microneedles 3 each have a conical structure,the diameter of the basal surface thereof is preferably about 50 to 200μm. Although the microneedles 3 are each in a conical shape according tothe present embodiment, microneedles may be in a polygonal pyramid shapesuch as a square pyramid or in other shapes.

The microneedles 3 are each typically disposed spaced apart so as tohave a density of approximately 1 to 10 needles per millimeter (mm) in arow of the needles. Generally, adjacent rows are spaced apart from eachother by a distance substantially equal to the space between the needlesin a row, and the microneedles 3 have a needle density of 100 to 10000needles per cm². When a needle density of 100 needles or more isachieved, the microneedles can efficiently pierce the skin. Meanwhile, aneedle density of more than 10000 needles makes it difficult to maintainthe strength of the microneedles 3. The density of the microneedles 3 ispreferably 200 to 5000 needles, more preferably 300 to 2000 needles, andstill more preferably 400 to 850 needles.

Examples of a material of the substrate 2 or the microneedles 3 includesilicon, silicon dioxide, ceramics, metals (such as stainless steel,titanium, nickel, molybdenum, chromium, and cobalt) and synthetic ornatural resin materials. In consideration of the antigenicity of themicroneedles and the unit price of the material, a biodegradable polymersuch as polylactic acid, polyglycolide, polylacticacid-co-polyglycolide, pullulan, caprolactone, polyurethane, andpolyanhydride, and a synthetic or natural resin material such aspolycarbonate, polymethacrylic acid, ethylenevinyl acetate,polytetrafluoroethylene, and polyoxymethylene, which are non-degradablepolymers, are particularly preferable. Further, polysaccharides such ashyaluronic acid, sodium hyaluronate, pullulan, dextran, dextrin, andchondroitin sulfate are also suitable.

Examples of a production method of the substrate 2 or the microneedles 3include wet etching process or dry etching process using a siliconsubstrate, precision machining using metals or resins (such as electricdischarge method, laser processing, dicing processing, hot embossingprocess, and injection mold processing), and machinery cutting. By theseprocessing methods, the substrate 2 and the microneedles 3 areintegrally molded. Examples of a method for hollowing the microneedles 3include a method in which a secondary processing such as laserprocessing is applied after producing the microneedles 3.

Although the microneedle device 1 has the coating layer 5 on each of themicroneedles 3, the coating layer 5 is preferably formed by coating withthe coating composition. Examples of the coating method include spraycoating and dip coating, and the dip coating is preferable. In thisregard, although the coating layer 5 is formed on all the microneedles 3in FIG. 1, the coating layer 5 may be formed on only some of themicroneedles 3. Although the coating layer 5 is formed on only the tipportion of the microneedle 3 in FIG. 1, the layer may be formed so as tocover the whole microneedle 3. Further, the coating layer 5 may beformed on the substrate 2.

FIG. 2 is a cross-sectional side surface view of FIG. 1 taken along theline II-II. As shown in FIG. 2, the microneedle device 1 has thesubstrate 2, the microneedles 3 disposed on the substrate 2, and thecoating layer 5 formed on each of the microneedles 3. The coating layer5 formed on each of the microneedles contains a physiologically activesubstance, arginine, and glycerin.

The mass of arginine contained in the coating layer is preferably 0.06to 0.85-fold, more preferably 0.1 to 0.65-fold, still more preferably0.1 to 0.5-fold of the mass of the physiologically active substance. Themass of arginine is 0.06-fold or more of the mass of the physiologicallyactive substance, whereby the occurrence of cracks in the coating layercan be reduced when the coating layer is formed. Consequently, theproductivity of the microneedle device is further improved.

Further, the mass of arginine contained in the coating layer ispreferably 0.1 to 40%, more preferably 3 to 33%, and still morepreferably 7 to 25% relative to the mass of the whole coating layer.

The mass of glycerin contained in the coating layer is 40% or less basedon the mass of the whole coating layer. From the viewpoint of practicalutility, it is 10% or more. Further, the mass of glycerin is preferably10 to 40%, more preferably 15 to 40%, and still more preferably 15 to35%.

The mass of glycerin contained in the coating layer is preferably 2-foldor less, more preferably 1.5-fold or less, and still more preferably1-fold or less of the mass of the physiologically active substance.

With respect to the mass of each of the components contained in thecoating layer, the content of glycerin is measured by, for example, gaschromatography, and based on its value, the content of other componentscan be calculated.

The coating layer can be formed using, for example, a coatingcomposition containing a physiologically active substance, arginine andglycerin.

The physiologically active substance is not particularly limited as longas it is a substance which exerts a therapeutic or prophylactic effectin a subject to be administered. Examples of the physiologically activesubstance include peptides, proteins, DNAs, RNAs, sugars, nucleic acids,and glycoproteins. Particularly, when the physiologically activesubstance is a glycoprotein, the coating layer can be formed moreefficiently.

Specific examples of the physiologically active substance includeinterferon-α, interferon-n for multiple sclerosis, erithropoietin,follitropin-β, follitropin-α, G-CSF, GM-CSF, human chorionicgonadotropin, leutinizing hormone, follicle stimulating hormone (FSH),calcitonin salmon, glucagon, GNRH antagonist, insulin, LHRH (lutealhormone releasing hormone), human growth hormone, parathyroid hormone,filgrastim, heparin, low molecular weight heparin, somatropin, incretin,GLP-1 analog (for example, exenatide, liraglutide, lixisenatide,albiglutide, and taspoglutide), venom peptide analog, γ-globulin,Japanese encephalitis vaccine, rotavirus vaccine, Alzheimer's diseasevaccine, arteriosclerosis vaccine, cancer vaccine, nicotine vaccine,diphtheria vaccine, tetanus vaccine, pertussis vaccine, Lyme diseasevaccine, rabies vaccine, diplococcus-pneumoniae vaccine, yellow fevervaccine, cholera vaccine, vaccinia vaccine, tuberculosis vaccine,rubella vaccine, measles virus vaccine, influenza vaccine, mumpsvaccine, botulinus vaccine, herpesvirus vaccine, other DNA vaccines, andhepatitis B vaccine.

The content of the physiologically active substance in the coatingcomposition is preferably 20 to 70% by mass, more preferably 25 to 50%by mass, and still more preferably 20 to 45% by mass based on the massof the whole coating composition. When the content of thephysiologically active substance is 20% by mass or more, apharmacological action of the physiologically active substance issufficiently exerted, thereby easily producing a desired therapeuticeffect.

The content of arginine in the coating composition is preferably 0.05 to2-fold, more preferably 0.05 to 1-fold, and still more preferably 0.1 to0.5-fold of the mass of the physiologically active substance containedin the coating composition. The content of arginine is 0.05-fold or moreof the mass of the physiologically active substance, thereby makingcracks in the coating layer less likely to occur. Further, the contentof arginine is 2-fold or less, thereby further improving the solubilityof the physiologically active substance in the coating composition.

The coating composition contains glycerin so that the content uniformityof the physiologically active substance in the coating composition underthe coating conditions (for example, room temperature) is improved.Here, the phrase “lack of content uniformity” means that when thecoating composition is applied to the microneedles, the content of thephysiologically active substance in the coating composition becomesnon-uniform with remarkable changes in physical properties of thecoating composition due to volatilization of a solvent (for example, aphenomenon such as generation of concentration gradient or impossibilityof applying to microneedles after drying). The content uniformity of thephysiologically active substance is improved, whereby thephysiologically active substance is stably released from the coatinglayer during the use of the microneedle device and a desired therapeuticeffect can be continuously obtained. Further, glycerin having a highviscosity is contained so that the coating layer is easily supported onthe tip of the microneedle. In this regard, glycerin is a component thatvolatilizes when reduced-pressure drying is performed. The glycerinitself does not solidify.

The content of glycerin in the coating composition is preferably 0.8 to2-fold, more preferably 1 to 2-fold, and still more preferably 1 to1.5-fold of the mass of the physiologically active substance containedin the coating composition. More preferred is a case in which thecontent of glycerin is 0.8-fold or more of the mass of thephysiologically active substance, because the content uniformity andsolubility of the physiologically active substance in the coating layerare excellent and the dripping is less likely to occur when beingapplied to the microneedles.

Further, the coating composition preferably contains an acid selectedfrom the group consisting of citric acid, phosphoric acid, boric acid,tartaric acid, and lactic acid. Particularly, the coating compositionmore preferably contains citric acid. The coating composition contains aspecific acid so that the basicity of arginine can be neutralized, andthe pH of the composition can be adjusted to a desired range.

The content of the acid is preferably 0.1 to 20% by mass, morepreferably 0.5 to 10% by mass, and still more preferably 1 to 7% by massbased on the mass of the whole coating composition.

Further, the content of the acid is preferably 0.01 to 1-fold, morepreferably 0.05 to 0.8-fold, and still more preferably 0.1 to 0.5-foldof the mass of arginine contained in the coating composition.

The coating composition may further contain a solvent, a polymericcarrier (thickening agent), a solubilizing agent, an absorptionpromoter, a stabilizer, an antioxidant, an emulsifier, a surfactant, anda compound such as a salt, as needed. Examples of the solvent includewater such as purified water and distilled water and alcohols such asmethanol and ethanol. The coating composition contains a solvent so thatthe handling properties when applied to the microneedles can be improvedand the solvent can be easily removed by the drying step.

When the coating composition contains a solvent, the solvent is removedin the drying step. Accordingly, the composition ratio of the componentsin the coating composition is not necessarily reflected in the coatinglayer.

Hence, when a microneedle device is produced, the coating layer isformed by drying the coating composition applied to the microneedles. Inthe drying step, the solvent contained in the coating composition isremoved and the content of glycerin may also decrease. Further, thecoating layer is formed by reduced-pressure drying, whereby the contentof glycerin decreases and the concentration of the physiologicallyactive substance contained in the coating layer tends to increase.

With respect to the time required to dry the applied coatingcomposition, the drying is preferably performed until the mass ofglycerin reaches 40% or less relative to the mass of the whole coatinglayer. Specifically, the mass of glycerin decreases, preferably by 25%or more, more preferably by 33% or more, and still more preferably by50% or more relative to the mass of glycerin contained in thecomposition applied to the microneedles. Further, the drying time ispreferably 1 hour or longer, the drying is performed more preferably for3 hours or longer, still more preferably 5 hours or longer, particularlypreferably 10 hours or longer, and extremely preferably 15 hours orlonger.

Examples of the polymeric carrier include polyethylene oxide,polyhydroxymethylcellulose, hydroxypropylcellulose,polyhydroxypropylmethylcellulose, polymethylcellulose, dextran,polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, pullulan,carmellose sodium, chondroitin sulfate, hyaluronic acid, dextran, andgum arabic. The weight average molecular weight of polyethylene glycolto be used as a polymeric carrier preferably exceeds 600 but is 500000or less. As the polymeric carrier, a carrier highly compatible (havingproperties of being uniformly mixed) with a physiologically activesubstance is preferable. Particularly preferred arehydroxypropylcellulose, dextran, polyvinyl alcohol, pullulan, and thelike.

The content of the polymeric carrier in the coating composition 10 is0.005 to 30% by mass, preferably 0.01 to 20% by mass, and morepreferably 0.05 to 10% by mass based on the total mass of the coatingcomposition 10. The polymeric carrier may need to have a certain degreeof viscosity that does not cause dripping and the viscosity ispreferably 100 to 100000 mPa·s at room temperature (25° C.). A morepreferable viscosity is 500 to 60000 mPa·s.

In addition to the above, to the coating composition 10, propylenecarbonate, crotamiton, L-menthol, peppermint oil, limonene, diisopropyladipate, and the like may be added as a solubilizing aid or absorptionpromoter, and methyl salicylate, glycol salicylate, L-menthol, thymol,peppermint oil, nonylic acid vanillylamide, chili pepper extract, andthe like may be added as an efficacy supplement as needed.

The surfactant may be either a nonionic surfactant or an ionicsurfactant (cationic, anionic, and amphoteric); however, from the safetyaspect, a nonionic surfactant, which is normally used for apharmaceutical base, is desirable. Examples of these compounds includesugar alcohol fatty acid ester such as sucrose fatty acid ester,propylene glycol fatty acid ester, polyoxyethylene sorbitan fatty acidester, polyoxyethylene glycerin fatty acid ester, polyethylene glycolfatty acid ester, polyoxyethylene castor oil, and polyoxyethylenehydrogenated castor oil.

A method for producing a microneedle device comprises the steps of:providing a microneedle array that has a substrate and a microneedle;mixing a physiologically active substance, arginine, and glycerin toobtain a coating composition; coating the microneedle with the coatingcomposition; and drying the coating composition to form a coating layeron the microneedle.

Subsequently, the method for producing a microneedle device will beexplained with reference to FIGS. 3(a) to 3(c). In this regard, theproduction method shown in FIGS. 3(a) to 3(c) is also referred to as“dip method using a mask plate”.

FIGS. 3(a) to 3(c) are pattern diagrams showing one embodiment of amethod for producing a microneedle device. According to this method,first of all, as shown in FIG. 3(a), the coating composition 10 is sweptwith a spatula 12 in the direction of the arrow A on a mask plate 11. Bydoing so, openings 13 are filled with the coating composition 10.Subsequently, as shown in FIG. 3(b), the microneedles 3 are insertedinto the openings 13 of the mask plate 11. Thereafter, as shown in FIG.3(c), the microneedles 3 are pulled out from the openings 13 of the maskplate 11. By doing so, the coating composition 10 adheres to themicroneedles 3. In this regard, the coating composition 10 may adhere tothe substrate 2. The volatile substance in the coating composition 10 onthe microneedles 3 is removed by a method such as air drying,reduced-pressure drying (vacuum drying), or a combination of thesemethods. By the above process, the coating layer 5 strongly adheres toeach of the microneedles 3, and typically becomes glassy or solid,whereby the microneedle device 1 is produced. The water content in thecoating layer 5 is normally 55% by mass or less, preferably 30% by massor less, and more preferably 10% by mass or less based on the totalamount of the coating layer 5. By the above method, dripping of thecoating composition 10 after being coated is prevented. The drippingindicates dripping of the coating composition from needle tips and meansthat an H part in FIG. 3(c) lengthens.

The height H of the coating layer 5 formed on each of the microneedles 3is adjusted by a clearance (gap) C shown in FIG. 3(b). This clearance Cis defined as a distance between the basal surface of the microneedles 3and the surface of the mask plate 11 (a thickness of the substrate 2 isnot involved), and is set according to a tension of the mask plate 11and the length of the microneedles 3. The range of the distance ofclearance C is preferably 0 to 500 μm. When a distance of clearance C is0, it means that the coating composition 10 is applied to the entiremicroneedles 3. Although the height H of the coating composition 10formed on the microneedles 3 varies depending on the height H of themicroneedles 3, the height H is normally 10 to 500 μm, preferably 30 to300 μm, and more preferably 40 to 250 μm. In order to effectivelyadminister the physiologically active substance in the coatingcomposition 10 to the skin, the substance is preferably concentrated ina part of the microneedle 3 (i.e., the tip portion of the microneedle3). From viewpoints of the stimulation to the skin and the transferringefficiency of the physiologically active substance to the skin, it ispreferable to allow the substance to be located at up to 200 μm from thetip of the microneedle 3. When the coating composition 10 has a highviscosity, the coating layer 5 is easily formed on a part of themicroneedle. By the method, the coating composition 10 adhering to themicroneedles 3 after removal of its volatile components can formpreferably an approximately spherical or teardrop shaped coating layer 5at the tip portion of the microneedle 3. Then, the coating compositionis inserted into the skin at the same time when the microneedles 3pierce the skin.

The thickness of the dried coating layer 5 is preferably less than 50μm, more preferably less than 40 μm, and still more preferably 1 to 30μm. Generally, the thickness of the coating layer 5 refers to an averagethickness as measured over the surface of the microneedle 3 afterdrying. The thickness of the coating layer 5 can be optionally increasedby applying a plurality of films of the coating composition 10, namely,by repeatedly performing the step of coating with the coatingcomposition 10.

When the microneedle 3 is coated with the coating composition 10,temperature and humidity in an installation environment of an apparatusare preferably controlled at a constant level. When the coatingcomposition 10 contains water, the environment may be filled with water,as needed. By doing so, evaporation of the water in the coatingcomposition 10 can be prevented as much as possible.

EXAMPLE

Hereinbelow, the present invention will be more specifically describedby providing Examples.

(1) Content Uniformity Test

The coating compositions of Reference Examples 1 to 4 prepared accordingto the description of Table 1 were applied to twenty microneedle sheetsby the dip method using a mask plate. In this regard, usedphysiologically active substances were dextran 40 (in Reference Examples1 and 3), γ-globulin (in Reference Example 2), and bovine serum albumin(BSA) (in Reference Example 4). As a tracer, benzoic acid was added toeach of Reference Examples for HPLC measurement. Each number in Table 1means mass percent relative to the whole coating composition.

Subsequently, the coating compositions applied to the microneedles wereindividually recovered. The content of benzoic acid in each of thecoating compositions was measured to calculate the content of thephysiologically active substance. The average, standard deviation (SD),and coefficient of variation (CV) of the content of the resultingphysiologically active substance were calculated. In this regard, thecoefficient of variation (CV) is a value obtained by dividing thestandard deviation by the average.

TABLE 1 Reference Reference Reference Reference Example 1 Example 2Example 3 Example 4 Dextran 40 49 — 29 — γ-globulin — 29 — — BSA — — —34 Glycerin — 52.5 52.5 48.75 Water 50 17.5 17.5 16.25 Benzoic acid 1 11 1 Total 100 100 100 100

The results are shown in Table 2. In the case of using the coatingcompositions of Reference Examples 2 to 4 containing glycerin, both thestandard deviation and coefficient of variation decreased, compared tothe case of using the coating composition of Reference Example 1.Therefore, it is considered that the coating composition containsglycerin so that the content uniformity of the physiologically activesubstance in the coating layer is improved.

TABLE 2 Reference Reference Reference Reference Example 1 Example 2Example 3 Example 4 Average [μg] 47.2 15.8 52.1 33.5 Standard deviation4.9 1.2 2.4 1.2 (SD) [μg] Coefficient of 10.3 7.3 4.7 3.7 variation (CV)[%]

(2) Influence of Content of Arginine

BSA, L-arginine, citric acid, glycerin, and water were mixed accordingto the description of Table 3 to prepare coating compositions ofExamples 1 to 9 and Comparative Example 1. In this regard, BSA was usedas the physiologically active substance. Each number in Table 3 means “%by mass”. Each of the obtained coating compositions was applied to thetip of the microneedle by the dip method using a mask plate.Subsequently, each of the applied coating compositions was dried underreduced pressure to form a coating layer. The content of glycerin in thecoating layer was quantified by gas chromatography (GC) analysis.Further, the property of the coating layer (crack state) was observedusing the digital microscope (KEYENCE CORPORATION.) and evaluated inaccordance with the following evaluation criteria:

<Evaluation Criteria>

Good: No cracks;

Poor: Any cracks are present on the surface; and

Bad: Any cracks are present on the surface and the coating layer ispartially chipped.

TABLE 3 L- Citric BSA arginine acid Glycerin Water Total Comparative50.0 — — 40.0 10.0 100.0 Example 1 Example 1 46.7 2.5 0.8 40.0 10.0100.0 Example 2 43.3 5.0 1.7 40.0 10.0 100.0 Example 3 40.0 7.5 2.5 40.010.0 100.0 Example 4 36.7 10.0 3.3 40.0 10.0 100.0 Example 5 33.3 12.54.2 40.0 10.0 100.0 Example 6 30.0 15.0 5.0 40.0 10.0 100.0 Example 726.7 17.5 5.8 40.0 10.0 100.0 Example 8 23.3 20.0 6.7 40.0 10.0 100.0Example 9 40.0 10.0 — 40.0 10.0 100.0

The results are shown in Table 4. In the cases of the coatingcompositions of Examples 1 to 9 containing L-arginine, the occurrence ofcracks was reduced during formation of the coating layer. The occurrenceof cracks was significantly reduced, particularly in the cases of thecoating compositions of Examples 2 to 9 having an L-arginine content of7.3% by mass or more. During preparation of the coating compositions ofExamples 1 to 7, the solubility of BSA, L-arginine, and citric acid in amixed solvent of glycerin and water (volume ratio 4:1) was moreexcellent.

TABLE 4 Content [% by mass] BSA L-arginine Glycerin Cracks Comparative74.8 0.0 25.2 x Example 1 Example 1 71.0 3.8 24.0 Δ Example 2 63.0 7.327.3 ∘ Example 3 62.4 11.7 22.0 ∘ Example 4 58.6 16.0 20.1 ∘ Example 554.5 20.4 18.3 ∘ Example 6 50.1 25.0 16.5 ∘ Example 7 44.1 29.0 17.2 ∘Example 8 39.1 33.5 16.3 ∘ Example 9 62.4 15.6 22.0 ∘

(3) Effect of Reducing Occurrence of Cracks

A physiologically active substance, L-arginine, citric acid, and aqueousglycerin were mixed according to the description of Table 5 to preparecoating compositions of Examples 10 to 13 and Comparative Examples 2 to5. In this regard, human serum albumin (HSA), lixisenatide, luteinizinghormone-releasing hormone (LHRH), or γ-globulin was used as thephysiologically active substance. Further, the used aqueous glycerin hasa weight ratio of water to glycerin of 20:80. Each number in Table 5means “% by mass”. Each of the obtained coating compositions was appliedto the tip of the microneedle by the dip method using a mask plate.Subsequently, each of the applied coating compositions was dried underreduced pressure to form a coating layer. The content of glycerin in thecoating layer was quantified by gas chromatography (GC) analysis.Further, the property of the coating layer (crack state) was observedusing the digital microscope (KEYENCE CORPORATION.) and evaluated inaccordance with the above evaluation criteria.

TABLE 5 Physiologically active substance Citric Aqueous Kind ContentL-arginine acid glycerin Comparative HSA 30.0 0.0 0.0 70.0 Example 2Example 10 HSA 30.0 3.5 1.2 65.3 Comparative Lixisenatide 40.0 0.0 0.060.0 Example 3 Example 11 Lixisenatide 40.0 4.6 1.5 53.9 ComparativeLHRH 50.0 0.0 0.0 50.0 Example 4 Example 12 LHRH 50.0 5.8 1.9 42.3Comparative γ-globulin 30.0 0.0 0.0 70.0 Example 5 Example 13 γ-globulin30. 3.5 1.2 65.3

The results are shown in Table 6. As shown in Table 6, when HSA,lixisenatide, LHRH or γ-globulin was used as the physiologically activesubstance, cracks were not generated in the coating compositions ofExamples 10 to 13 containing L-arginine and citric acid during formationof the coating layer. Meanwhile, cracks were generated in the coatingcompositions of Comparative Examples 2 to 5 which did not containL-arginine and citric acid during formation of the coating layer.

TABLE 6 Content ratio of L-arginine to Content physiologically active[%] of substance glycerin Cracks Comparative — 13.2 x Example 2 Example10 0.12 17.9 ∘ Comparative — 15.4 x Example 3 Example 11 0.12 19.7 ∘Comparative — 23.0 x Example 4 Example 12 0.12 28.1 ∘ Comparative — 11.2x Example 5 Example 13 0.12 13.6 ∘

The coating compositions of Examples 14 to 20 were prepared according tothe description of Table 7.

TABLE 7 Physiologically active substance Citric Aqueous Kind ContentL-arginine acid glycerin Comparative Parathyroid 40.0 5.0 1.5 53.5Example 14 hormone Comparative GLP-1 analog 40.0 5.0 1.5 53.5 Example 15Comparative Interferon-β 40.0 5.0 1.5 53.5 Example 16 Comparative Lowmolecular 40.0 5.0 1.5 53.5 Example 17 weight heparin Comparative Venompeptide 40.0 5.0 1.5 53.5 Example 18 analog Comparative Influenza 40.05.0 1.5 53.5 Example 19 vaccine Comparative Cancer vaccine 40.0 5.0 1.553.5 Example 20

(4) Content Uniformity Test

The coating composition of Example 21 prepared according to thedescription of Table 8 was applied to twenty microneedle sheets by thedip method using a mask plate. In this regard, bovine serum albumin(BSA) was used as the physiologically active substance and a tracer(fluorescein sodium) was added thereto for measurement with afluorescence plate reader. Further, each number in Table 8 means masspercent relative to the whole coating composition.

Subsequently, the coating compositions applied to microneedles wererespectively recovered. The content of fluorescein sodium in each of thecoating compositions was measured to calculate the content of thephysiologically active substance. The average, standard deviation (SD),and coefficient of variation (CV) of the content of the resultingphysiologically active substance were calculated. In this regard, thecoefficient of variation (CV) is a value obtained by dividing thestandard deviation by the average.

TABLE 8 Example 21 BSA 30 Glycerin 60 Arginine 5 Water 15 Fluoresceinsodium 0.05

The results are shown in Table 9. The formation of the coating layerusing the coating composition of Example 21 resulted in an improvementof the content uniformity of the physiologically active substance in thecoating layer.

TABLE 9 Example 21 Average [μg] 36.7 Standard deviation (SD) 2.6 [μg]Coefficient of variation 7.2 (CV) [%]

(5) Effect of Reducing Occurrence of Cracks

A physiologically active substance, L-arginine, acid, and aqueousglycerin were mixed according to the description of Tables 10 and 11 toprepare coating compositions of Examples 25 to 32. In this regard, humanserum albumin (HSA), lixisenatide, luteinizing hormone-releasing hormone(LHRH) or γ-globulin was used as the physiologically active substance,and phosphoric acid or tartaric acid was used as the acid. Further, theused aqueous glycerin has a weight ratio of water to glycerin of 20:80.Each number in Tables 10 and 11 means “% by mass”. Each of the obtainedcoating compositions was applied to the tip of the microneedle by thedip method using a mask plate. Subsequently, each of the applied coatingcompositions was dried under reduced pressure to form a coating layer.The content of glycerin in the coating layer was quantified by gaschromatography (GC) analysis. Further, the property of the coating layer(crack state) was observed using the digital microscope (KEYENCECORPORATION.) and evaluated in accordance with the above evaluationcriteria.

TABLE 10 Physiologically active Phosphoric Aqueous substance Arginineacid glycerin Example 25 HSA 30 3.5 1.2 65.3 Example 26 Lixisenatide 404.6 1.5 53.9 Example 27 LHRH 50 5.8 1.9 42.3 Example 28 γ-globulin 303.5 1.2 65.3

TABLE 11 Physiologically active Tartaric substance Arginine acidGlycerin Example 29 HSA 30 1.5 1.2 65.3 Example 30 Lixisenatide 40 4.61.5 53.9 Example 31 LHRH 50 5.8 1.9 42.3 Example 32 γ-globulin 30 3.51.2 65.3

The results are shown in Table 12. No cracks were generated in all thecoating layers prepared from the coating compositions of Examples 25 to32.

TABLE 12 Content ratio of L-arginine Content to physiologically active[%] of substance glycerin Cracks Example 25 0.12 16.3 ∘ Example 26 0.1221.8 ∘ Example 27 0.12 22.6 ∘ Example 28 0.12 18.6 ∘ Example 29 0.1216.6 ∘ Example 30 0.12 26.8 ∘ Example 31 0.12 26.6 ∘ Example 32 0.1217.9 ∘

REFERENCE SIGNS LIST

1 . . . Microneedle device, 2 . . . Substrate, 3 . . . Microneedle, 5 .. . Coating layer, 10 . . . Coating composition, 11 . . . Mask plate, 12. . . Spatula, 13 . . . Opening.

1-9. (canceled)
 10. A method for producing a microneedle devicecomprising the steps of: providing a microneedle array comprising asubstrate and a microneedle; mixing a physiologically active substance,arginine, and glycerin to obtain a coating composition; coating themicroneedle with the coating composition; and drying the coatingcomposition to form a coating layer on the microneedle.
 11. The methodaccording to claim 10, wherein the coating composition further containsan acid selected from the group consisting of citric acid, phosphoricacid, boric acid, tartaric acid, and lactic acid.
 12. The methodaccording to claim 10, wherein the drying is performed until, in thecoating layer, the mass of arginine reaches 0.06 to 0.85-fold of themass of the physiologically active substance and the mass of glycerinreaches 40% or less relative to the mass of the whole coating layer. 13.The method according to claim 11, wherein the drying is performed until,in the coating layer, the mass of arginine reaches 0.06 to 0.85-fold ofthe mass of the physiologically active substance and the mass ofglycerin reaches 40% or less relative to the mass of the whole coatinglayer.